Hi folks, My A8 just overheated, managed to get it to the garage. They replaced the thermostat and the water pump. So far so good - all working again. Today I noticed the expansion tank is hissing after a run. Prior to the overheat incident I could hear a lot of water sloshing about in the air-con outlets. I manged to pump out about 2 pints of water from the rear seat vent! The water in the air-con is more like rain water - no anti-freeze or grubby water, all clean. I am most concerned about the expansion tank problem. Any of this make any sense? Best. Barry.